IP-based mobile systems provide for communication between at least one mobile node and a wireless communication network. The term “mobile node” includes a mobile communication unit (e.g., mobile terminal, “smart phones”, nomadic devices such as laptop PCs with wireless connectivity, as described in greater detail below). Among other elements, the wireless communication system includes a home network and a foreign network. The mobile node may change its point of attachment to the Internet through these networks, but the mobile node will always be associated with a single home network for IP addressing purposes. The home network includes a home agent and the foreign network includes a foreign agent—both of which control the routing of information packets into and out of their network. Generally, there may also be a correspondence node associated with the system, which may be a mobile or fixed node located on one of the networks that communicates with the mobile node.
The mobile node, home agent and foreign agent may be called different names depending on the nomenclature used on any particular network configuration or communication system. For instance, a “mobile node” encompasses PC's having cabled (e.g., telephone line (“twisted pair”), Ethernet cable, optical cable, and so on) connectivity to the wireless network, as well as direct wireless connectivity to the cellular network. Direct wireless connectivity to a cellular network is supported by various makes and models of mobile terminals (“cell phones”) having various features and functionality, such as Internet access, e-mail, messaging services, and the like. Mobile nodes are sometimes called a user equipment, mobile unit, mobile terminal, mobile device, or similar names depending on the nomenclature adopted by particular system providers.
A home agent may also be referred to as a local mobility anchor, home mobility manager, home location register, and a foreign agent may be referred to as a mobile access gateway, serving mobility manager, visited location register, and visiting serving entity. The terms mobile node, home agent and foreign agent are not meant to be restrictively defined, but could include other mobile communication units or supervisory routing devices located on the home or foreign networks. Foreign networks can also be called serving networks.
Registering the Mobile Node
Foreign agents and home agents periodically broadcast an agent advertisement to all nodes on the local network associated with that agent. An agent advertisement is a message from the agent on a network that may be issued under the Mobile IP protocol (RFC 2002) or any other type of communications protocol. This advertisement should include information that is required to uniquely identify a mobility agent (e.g. a home agent, a foreign agent, etc.) to a mobile node. Multiple interfaces may also be supported on a single or multiple foreign networks, which can include the different communication access types 802.11d, 802.11g, HRPD, WiFi, WiMax, CDMA, or LTE. Mobile nodes examine the agent advertisement and determine whether they are connected to the home network or a foreign network.
The mobile node will always be associated with its home network and sub-network for IP addressing purposes and will have information routed to it by routers located on the home and foreign network. If the mobile node is located on its home network, information packets will be routed to the mobile node according to the standard addressing and routing scheme.
If the mobile node is visiting a foreign network, however, the mobile node obtains appropriate information from the agent advertisement, and transmits a registration request message (sometimes called a binding update request) to its home agent through the foreign agent. The registration request message will include a care-of address for the mobile node. A registration reply message (also called a binding update acknowledge message) may be sent to the mobile node by the home agent to confirm that the registration process has been successfully completed.
Care-of Addressing and Discontinuity Problems
As part of the registration process, the mobile node maintains connectivity with the home agent or local mobility anchor through the use of a “care-of address.” This care-of address is registered with the home agent or local mobility anchor in a table, sometimes called a Binding Cache Entry Table. The registered care-of address identifies the foreign network where the mobile node is located, and the home agent or local mobility anchor uses this registered care-of address to forward information packets to the foreign network for subsequent transfer onto the mobile node.
If the home agent or local mobility anchor receives an information packet addressed to the mobile node while the mobile node is located on a foreign network, the home agent or local mobility anchor will transmit the information packet to the mobile node's current location on the foreign network using the applicable care-of address. This is accomplished by forwarding the information packet to the care-of address where the foreign network will receive the information packet, and forward the information packet to the mobile node on the foreign network. During these communications, the transmission of communication packets between the foreign network and the home agent or local mobility anchor will be performed using a tunneling communication protocol.
The registered care-of address identifies the foreign network where the mobile node is located, and the home agent or local mobility anchor also uses this registered care-of address to forward information packets received from the mobile node located on the foreign network. In this situation, the mobile node may transmit information and communication packets back through the foreign agent to the home agent or local mobility anchor for further processing and transmission to other nodes on the system, such as the correspondence node. The source of the information packets will be identified on the mobile node's packets as the mobile node's care-of address.
The home agent or local mobility anchor will confirm that the mobile node's communications are being transmitted from a valid care-of address for the mobile node before routing, processing, and further transferring the packets received from the mobile node. If the home agent receives an information packet that does not have a valid care-of address as its source, the packets will not be processed further. If the care-of address is valid, the information packet will then be forwarded and routed to the destination by the home agent or local mobility anchor. These communications are sometimes referred to a “tunneled” communication between the foreign network and the home network.
A mobile node may transition and move from one foreign network to another foreign network. Each foreign network is identified by a different care-of address, so the transition of the mobile node from one foreign network to a new foreign network requires a modification of the care-of addresses registered for the mobile node at the home agent or local mobility anchor. During this modification of the care-of addressing resulting from the mobile node transition from one foreign network to another foreign network, problems are sometimes encountered with the maintaining the continuity of the tunneled message transmissions to and from the mobile node through the home agent or local mobility anchor.
For instance, messages addressed to the new care-of address for the new foreign network may not be properly transmitted to the mobile node by the home agent or local mobility anchor until the hand-off to the new foreign network has been fully completed. In fact, prior to the hand-off to the new foreign network being fully completed, communication packets addressed to the new foreign network may be dropped or communication packets may be misdirected to the old foreign network care-of address, both of which will result in a disruption of the continuity of the communication to the mobile node.
Moreover, mobile node information and communication packets being sent from the new foreign network may not be properly recognized because the care-of addressing for the new foreign network has not been registered with the home agent or local mobility anchor. In this situation, the home agent or local mobility anchor may refuse to accept communication packets from the mobile node on the new foreign network prior to the hand-off being fully completed to the new foreign network because the care-of address for the new foreign network is not recognized by the home agent or local mobility anchor as a valid source for such communication packets. These continuity problems cause communication disruption, dropped packets and interruption in continuous service. It is a primary objective of this invention to provide care-of addressing support and continuity of tunneled communication to and from a mobile node where the handover to a new foreign network is being initiated.